The present invention relates to the treatment of individuals with attention-deficit hyperactivity disorder with an anti-epileptic mood stabiliser (AEDMS), optionally in combination with psychostimulants, for example to improve psychosocial and cognitive function in such individuals. The present invention also relates to the treatment of individuals with other DSM-IV-TR classified disorders, such as autistic spectrum disorders. The present invention further relates to the treatment of learning difficulties, such as reading difficulties.
Attention-deficit hyperactivity disorder (ADHD) is a developmental disorder distinguished by symptoms of inattention, hyperactivity and impulsivity (Snyder, Nussbaum, & Robins (Eds.), 2006, Clinical Neuropsychology: A Pocket Handbook for Assessment, APABooks, Washington D.C.). Although ADHD is one of the most frequently diagnosed psychological disorders in childhood long-term studies have demonstrated that symptoms can be maintained into adulthood. The number of children and adolescents who maintain ADHD symptoms and continue their treatment as adults ranges from 36% to 65%. Data derived from longitudinal studies suggest that although the symptom cluster of hyperactivity and impulsivity decays over time, the symptoms of inattention persist and the proportion of clinically referred adults with ADHD endorsing prominent inattentive symptoms may be as high as 90%. Adult ADHD has now been recognised as a valid clinical entity that is associated with profound psychosocial and cognitive impairments (Weiss & Murray, 2003, CMAJ. 168(6): 715-22).
Studies of children and adults with ADHD indicate that many experience an array of cognitive impairments that extend beyond the behavioural symptoms outlined in the diagnostic criteria for the disorder (DSM-IV-TR; American Psychiatric Association, 2000). Higher level cognitive and information processing impairments have been reported, the functional day-to-day implications of which include chronic difficulties in maintaining alertness, self-discipline, establishing and keeping routines, and completing tasks. Adults with ADHD change jobs more often, accrue more speeding tickets and have more vehicle accidents than adults without the disorder.
It is well established that ADHD can occur with learning disorders (LD) in children at a rate substantially above chance levels, typically ranging between 25% and 40%. It is also becoming evident that for both ADHD and LD the underlying cognitive impairments seem to persist in a life span perspective. One recent study has examined the co-morbidity between ADHD and LD in an adult population. Samuelsson et al., 2004 (J. Learn. Disabil. 37(2):155-68) found no differences between adults with and without ADHD on measures of either phonological processing skills or word decoding; however adults with ADHD performed significantly worse on tests of reading comprehension than those who did not have ADHD. Samuelsson et al. concluded that the results are consistent with the view that reading comprehension involves many of the higher cognitive control functions thought to be impaired in ADHD.
The primary psychopharmacological agents used to treat ADHD are the CNS stimulants (pyschostimulants). Studies of the short term beneficial effects of stimulants on the symptoms of ADHD constitute the largest body of treatment literature of any childhood-onset psychiatric disorder, with the stimulant medications proven effective across diverse age and diagnostic groups. Until August 2005, the only stimulant available under the Australian Pharmaceutical Benefits Scheme (PBS) was dexamphetamine, explaining its predominant place in Australia for the treatment of ADHD. The PBS has since added methylphenidate to the subsidised listing, the most commonly used CNS stimulant in the US for the treatment of ADHD.
In both children and adolescents, stimulants can provide robust improvement in ADHD behavioural symptoms. Despite this, there is continued functional impairment in patients. In adults this was particularly evident in the area which is often referred to as higher executive function. This includes the ability to sequence, organise and integrate cognitive functioning and appears to be used during the complex interpersonal interaction which forms the basis of human social communication: any impairment in this area is quickly detected by almost every individual although it may not be easily identified or described. The use of stimulant medication enables a reduction in the motivation and effort required to complete a task, but they do not appear to enable the individual to make the complex task easier with repeated exposure. Thus the inevitable fatigue that comes from this is not counterbalanced by improved efficiency and eventually the task is ceased.
This same model can be applied to social interaction. For example, we have noted that the tendency to hyper-focus on a specific topic during conversation did not reduce consistently on stimulants alone, as it would appear that the individual could not process simultaneously the multiple lines of thought that usually take place in normal social interaction. Instead there would be the selection of a preferred more comfortable, possibly more familiar topic and as consequence, resistance to follow the natural flow of the conversation. Thus providing sufficient motivation exists, conversation can occur, but it still requires considerable effort and is often observed by the listener as awkwardness during the interaction and the individual will inevitably, in time, fatigue due to the effort involved. This results in a similar, although delayed, experience of mental exhaustion and failure to sustain attention that existed prior to the commencement of stimulants. Thus, we have observed that unless there is an improvement in the ability to process information, the improved motivation provided by the stimulant will inevitably wane. This is seen clinically with adults with a diagnosis of ADHD treated with stimulants; the initial and at times miraculous improvement frequently gives way to an increasing disorganisation, noncompliance with medication and an eventual ceasing of treatment.
Accordingly, there is a need for an improved treatment for ADHD, which is better, able to reduce the impairment in the underlying cognitive process seen in ADHD patients.